Heterocyclic compounds produced from biomass

ABSTRACT

Sugars derived from acidic hydrolysis of biomass consist of glucose and xyloses which are subjected to dehydration, within the hydrolysis environment, to form heterocyclic compounds, furfural and hydroxymethylfurfural. By providing a vessel for hydrolysis of biomass, a hydrolysate containing acid and heterocyclic compounds is formed. Upon withdrawing the hydrolysate from the vessel, and employment of separating means for removing heterocyclic compounds from the hydrolysate, a hydrolysate substantially devoid of heterocyclic compounds is provided for recycle to the vessel and will provide heterocyclic compounds. By withdrawing solids, containing lignins remaining from hydrolysis of biomass, from the vessel, and filtering the solids, to result in a filtrate for recycle to the vessel and provide filtered solids for subsequent processing. Thereby, heterocyclic compounds are derived from a biomass and withdrawn from the hydrolysis vessel, and solids, remaining from hydrolysis of biomass, are withdrawn from the hydrolysis vessel.

BACKGROUND OF THE INVENTION

[0001] Present day interest in hydrolysis of biomass is to provide analternative fuel source to avoid dependence on unreliable importedpetroleum crude oil for liquid fuels. Characteristic dry biomasscomposition is: lignin 25%, hemicellulose 25%, amorphous cellulose 10%,and crystalline cellulose 40%. Biomass is selected from the groupconsisting of wood, waste paper and municipal solid waste including anindividual or a combination thereof.

[0002] Acid for hydrolysis is selected from the group consisting ofinorganic acids and organic acids including sulfuric acid.

[0003] Furfural is produced by hydrolysis of hemicellulose to producepentose sugars subjected to dehydration to form furfural. Furfural isundesired in a hydrolysate for fermentation because furfural ofsufficient concentration in the hydrolysate will substantially inhibitgrowth of microorganisms required for fermentation, professed bySherman, et al., in U.S. Pat. No. 4,612,268.

[0004] A hydrolysate containing hydroxymethylfurfural derived fromdehydration of glucose formed by hydrolysis of a biomass, decreasescontents of glucose for fermentation. The unwanted effect ofhydroxymethylfurfural and furfural, within the hydrolyzate, in providinginhibition of fermentation to produce ethanol within fermentation iscontributed by Larsson, et al., on the internet, entitled “Thegeneration of fermentation inhibitors during dilute acid hydrolysis ofsoftwood”.

[0005] A state of the art process “process for preparing pure5-hydroxymethylfuraldehyde” is described by Rapp, in U.S. Pat. No.4,740,605, wherein saccharides are acid catalyzed to form HMF followedby extraction and chromatography to purify HMF.

[0006] It is therefore an object of this invention to obviate many ofthe limitations or disadvantages of the prior art.

[0007] The present concern is about producing heterocyclic compoundsfrom a biomass.

[0008] A distinct object of this invention is to provide liquid fuelsfrom a biomass without depending on fermentation.

[0009] Still another object of this invention is to provide heterocycliccompounds derived from acidic hydrolysis of a biomass.

[0010] Yet another object of this invention is to withdraw solids,containing lignins, from a biomass.

[0011] With the above and other objects in view, this invention relatesto the novel features and alternatives and combinations presentlydescribed in the brief description of the invention.

APPLICATIONS AND BACKGROUND OF THE INVENTION

[0012] Heterocyclic compounds such as furfural and hydroxymethylfurfuralare derived from acidic hydrolysis of biomass. Heterocyclic compoundshaving five rings of four carbon atoms and one oxygen atom consisting offurfural and hydroxymethylfurfural are described in Organic Chemistry,1948, authored by Hill and Kelley, page 778 and pages 780-781 Acidichydrolysis of biomass, containing hemicellulose and cellulose, formxyloses and glucose which are respectively subjected to dehydration,within the hydrolysis environment, to form heterocyclic compounds,furfural and hydroxymethylfurfural.

[0013] Hydrolysis of lignocellulose (biomass) kinetics for formation ofhydroxymethylfurfural and furfural is described in “High temperatureacid hydrolysis of cellulose for alcohol fuel production” by John D.Wright, prepared under task No. 3491 by the solar research institute,Golden Colo., for publication by the American Chemical Society Meeting,Aug. 28 to Sep. 2, 1983, page 2. Hydroxymethylfurfural and furfural,within a hydrolyzate, are undesirable compounds accompanying sugars andmust be separated prior to fermentation, so stated.

[0014] Solvents to dissolve hydroxymethylfurfural and furfural aredisclosed in the Merck index, eighth edition, 1968, page 552. Organicsolvents capable of dissolving heterocyclic compounds referred toinclude ether, benzene and chloroform. A solvent capable of dissolvingheterocyclic compounds and insoluble in aqueous solutions is selectedfrom the group consisting of organic solvents and cyclic compoundsincluding an individual or a combination thereof If chloroform, forexample, is employed as a solvent for extraction, a hydrolysatecontaining the solvent or a solution containing the solvent andhydroxymethylfurfural and furfural is formed. Distillation likely formsan azeotrope which can then utilized to recover solvent from the ensuingazeotrope, by condensation of two layers and separation of the layerrich in solvent and subjecting the layer poor in solvent todistillation. Formation of a binary chloroform and water azeotrope isdisclosed in the Handbook of Chemistry and Physics, 56th edition,1975-1976, page D-14.

[0015] An example of using furfural as a solvent is described on page840, in Chemical Process Industries, second edition, authored by R. N.Shreve, in which furfural is employed to dissolve lube oil to produce asolution for subsequent separation.

BRIEF DESCRIPTION OF THE INVENTION

[0016] The present invention, in its broadest aspect, comprises a methodto form heterocyclic compounds from a biomass which constitutesproviding a vessel for hydrolysis, and providing a biomass to thevessel. Thereupon subjecting biomass to hydrolysis within the vessel, toform glucose and xyloses which are subjected to dehydration, within thehydrolysis environment, to form heterocyclic compounds, furfural andhydroxymethylfurfural within a hydrolysate, containing acid andheterocyclic compounds. Hydrolysate, formed by hydrolysis, is withdrawnfrom the vessel, and subjected to separating means for dividingheterocyclic compounds to provide a hydrolysate substantially devoid ofheterocyclic compounds for recycle. Solids, remaining from hydrolysis ofbiomass, is removed from the vessel. The removed solids are subjected tofiltering resulting in a filtrate of a hydrolysate for recycle andfiltered solids, remaining from hydrolysis of biomass, subjected tosubsequent processing.

[0017] Characteristics of the invention include,

[0018] Sugars obtained by hydrolysis are susceptible to dehydration toform hydroxymethylfurfural and furfural.

[0019] Heterocyclic compounds are derived from a biomass by hydrolysiswithin a vessel.

[0020] Hydrolysate, formed by hydrolysis, is withdrawn from the vessel,

[0021] Solids, remaining from hydrolysis of biomass, containing lignins,is removed from the vessel

[0022] The method is customarily accomplished in a continuous fashion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The features that are considered characteristic of this inventionare set forth in the appended claims. This invention, however, both asto its origination and method of operations as well as additionaladvantages will best be understood from the following description whenread in conjunction with the accompanying drawings in which:

[0024]FIG. 1 is a flow sheet denoting the invention as set forth in theappended claims.

[0025]FIG. 2 is a flow sheet denoting a method to extract acid fromhydrolysis residue.

[0026]FIG. 3 is a flow sheet denoting a method to produce heterocycliccompounds from a cooled hydrolysate by extraction.

[0027]FIG. 4 is a flow sheet denoting a method to produce heterocycliccompounds from a cooled hydrolysate by adsorption.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] The flow diagram of FIG. 1 illustrates the general preferredembodiment of the present invention. In the diagram, rectanglesrepresent stages, operations or functions of the present invention andnot necessarily separate components. Details within each stage,operations or functions are not shown. Arrows indicate direction of flowof material in the method. Temperature control is maintained within thevessel from about 100° C. to about 250° C. to sustain hydrolysis. Acidfor hydrolysis is sulfuric acid at a concentration ranging from of 1 to10%.

[0029] Referring to FIG. 1, a method is depicted to form heterocycliccompounds by hydrolysis of a biomass. Biomass 10 is conveyed tohydrolysis stage 12 and subjected to hydrolysis, forming a hydrolysate14, which is withdrawn from the hydrolysis stage 12 and conveyed to heatexchanger stage 16 wherein heat is exchanged from hydrolysate 24 toconvey heated hydrolysate 26 to the hydrolysis stage 12. Cooledhydrolysate 18 is forwarded to separation stage 20 to separateheterocyclic compounds 22 from cooled hydrolysate 18 to be forwarded toheat exchange stage 16. Details of the separation stage 20 areextraneous to the function and are therefore omitted from FIG. 1. Cooledheat exchanged hydrolysate 18 is subject to additional treatment withinFIG. 3 and FIG. 4. Hydrolysis residue 28 from hydrolysis stage 12 isconveyed to filter stage 30 and subjected to filtration to producefiltrate 34 and filtered hydrolysis residue 32. Filtrate 34 is recycledand conveyed to hydrolysis stage 12. Filtered hydrolysis residue 32 issubject to additional treatment within FIG. 2. Hydrolysis residue 32will typically contain lignins The disclosed method is customarilyaccomplished in a continuous fashion.

[0030] Referring to FIG. 2, filtered hydrolysis residue 32 is conveyedto extraction stage 34 and extracted to produce an extractate 38 andextracted hydrolysis residue 32A. Extractate 38 conveyed to neutralizestage 40 is neutralized by addition of calcium carbonate 36 to create asolution containing calcium sulfate 42 and is conveyed to settle stage44 to settle and produce gypsum 46 and water 36, settled from gypsum,for recycle to extraction stage 34. Gypsum 46, upon settling, is removedfrom the settle stage 44 and is discarded. Water 36, settled fromgypsum, contains dissolved calcium sulfate and is conveyed to extractionstage 34. Extracted hydrolysis residue 32A, is substantially devoid ofacid but contains a trace of dissolved calcium sulfate. The filteredsolids containing acid are substantiality neutralized by chemicalsselected from the group consisting of inorganic bases and inorganicsalts including an individual or a combination thereof.

[0031] Referring to FIG. 3, cooled hydrolysate 18 is conveyed toextraction stage 48 and is extracted by a solvent 46A, insoluble inwater but soluble in heterocyclic compounds, to produce extractate 46and extracted hydrolysate 24 to be recycled to heat exchanger stage 16.The solvent 46A is often an organic halide. Extractate 46 is conveyed toextraction stage 54 to be extracted by water 50 to form a solution ofheterocyclic compounds 52. Extracted solvent 46A, insoluble in water butsoluble in heterocyclic compounds, is recycled to extraction stage 48.The solution of heterocyclic compounds 52 likely contains a solventwhich is then separated from the solution of heterocyclic compounds bydistillation.

[0032] Referring to FIG. 4, cooled hydrolysate 18 is conveyed toadsorption stage 56 and is adsorbed to produce an adsorbate,substantially devoid of heterocyclic compounds, of adsorbed hydrolysate24 to be recycled to heat exchanger stage 16 to conclude adsorptionpart 1. In batch fashion, adsorption part 2 employs the same adsorptionstage 56 to become adsorbed heterocyclic compounds stage 56. Adsorbedheterocyclic compounds stage 56, treated by water 58, frees heterocycliccompounds form the adsorbed heterocyclic compounds stage 56 to form asolution of heterocyclic compounds 60. The desorbed adsorbent requiredin adsorption stage 56 is reactivated to continue adsorption withinadsorption stage 56. The adsorbent, capable of adsorbing heterocycliccompounds, is selected from the group consisting of activated charcoal,fullers earth and alumina including an individual or a combinationthereof Accordingly the adsorption and desorption operations areaccomplished batch ways.

What is claimed is:
 1. A method to produce sugars from a biomass byhydrolysis and subject the sugars to dehydration to form heterocycliccompounds which comprises: providing a vessel for said hydrolysis withan acid, and providing a biomass to said vessel, and subjecting saidbiomass, within said vessel, to said hydrolysis and reaction within saidacid to form a hydrolysate, containing said heterocyclic compounds andsaid acid, and withdrawing said hydrolysate from said vessel, andseparating means for removing said heterocyclic compounds from saidhydrolysate to provide a hydrolysate substantially devoid ofheterocyclic compounds for recycle to said vessel and heterocycliccompounds for subsequent processing, and withdrawing solids, remainingfrom said hydrolysis of said biomass, from said vessel, and filteringsaid solids resulting in a filtrate for recycle to said vessel andfiltered solids, for subsequent processing, thereby removingheterocyclic compounds, derived from a biomass, from said vessel andremoving solids remaining from hydrolysis of biomass from said vessel.2. The method of claim 1 wherein said separating means is extraction bya solvent capable of dissolving said heterocyclic compounds forming anextractate of a hydrolysate substantially devoid of heterocycliccompounds for recycle to said vessel
 3. The method of claim 2 whereinsaid solvent capable of dissolving said heterocyclic compounds andinsoluble in aqueous solutions is selected from the group consisting oforganic solvents and cyclic compounds including an individual or acombination thereof.
 4. The method of claim 2 wherein said solventcapable of dissolving the heterocyclic compounds is an organic halide.5. The method of claim 1 wherein said filtered solids containing acidare substantiality neutralized by chemicals selected from the groupconsisting of inorganic bases and inorganic salts including anindividual or a combination thereof.
 6. The method of claim 1 whereinsaid filtered solids containing acid are substantiality neutralized byaddition of calcium carbonate.
 7. The method of claim 1 wherein saidheterocyclic compounds include hydroxymethylfurfural and furfural. 8.The method of claim 1 wherein said heterocyclic compounds are derivedfrom hemicellulose contained in said biomass.
 9. The method of claim 1wherein said biomass forms hydroxymethylfurfural from cellulosecontained within said biomass.
 10. The method of claim 1 wherein saidacid for said hydrolysis is selected from the group consisting ofinorganic acids and organic acids including an individual or acombination thereof.
 11. The method of claim 1 wherein said acid forsaid hydrolysis is sulfuric acid.
 12. The method of claim 1 wherein saidacid for said hydrolysis is sulfuric acid at a concentration rangingfrom of 1 to 10%.
 13. The method of claim 1 wherein said solidsremaining from said hydrolysis contain lignins derived from a biomass.14. The method of claim 1 wherein said separating means is an adsorbentcapable of adsorbing said heterocyclic compounds forming a hydrolysatesubstantially devoid of heterocyclic compounds for recycle to saidvessel and adsorbed heterocyclic compounds
 15. The method of claim 14wherein said adsorbed heterocyclic compounds is desorbed by waterforming a solution of heterocyclic compounds and adsorbent.
 16. Themethod of claim 14 wherein said adsorbent is selected from the groupconsisting of activated charcoal, fullers earth and alumina including anindividual or a combination thereof.
 17. The method of claim 1 whereinsaid hydrolysis is subjected to temperature control. to sustainhydrolysis.
 18. The method of claim 1 wherein said biomass is selectedfrom the group consisting of wood, waste paper and municipal solid wasteincluding an individual or a combination thereof.
 19. The method ofclaim 1 wherein said heterocyclic compounds are liquid fuels derivedfrom a biomass.
 20. The method of claim 1 wherein said method isaccomplished in a continuous fashion.